1. Field of the Invention
This invention relates to an apparatus for vapor drying of objects, and more particularly to a vapor drying apparatus for semiconductor wafers.
To be more specific, this invention relates to a vapor drying apparatus for semiconductor wafers, which is capable of preventing dust particles from entering the interior of the vapor drying apparatus incorporating therein a semiconductor wafer cleaning part and, at the same time, thoroughly removing from the surface of a vapor dried semiconductor wafer the vapor cleaner adhering in the form of film or in a molecular thickness to the surface or an organic substance contained in the cleaner thereby bringing the surface of the semiconductor wafer to an ideally cleaned and dried state.
2. Description of the Prior Art
It has been generally held that the process for manufacture of semiconductor wafers such as of silicon (hereinafter referred to simply as "wafers") necessitates incorporation of a step of cleaning subsequently to the step of chemical treatment of wafers. In this step of cleaning, it is necessary for the vapor drying apparatus first to admit a carrier supporting thereon a chemically treated wafer through a wafer insertion door thereof. Heretofore, the opening and closing of this door and the insertion of the aforementioned carrier have been manually carried out.
Then, the wafer-supporting carrier so inserted in the interior of the vapor drying apparatus is lifted by an automatically controlled movable hanger and immersed in deionized water (hereinafter referred to as "DI water") for cleaning of the wafer. Thereafter, the wafer as supported on the carrier is transported by the movable hanger into a vapor cleaning tank.
This vapor cleaning tank is a quartz container holding therein a prescribed amount of a volatile cleaning liquid [such as, for example, isopropyl alcohol (hereinafter referred to as "IPA")]. The aforementioned IPA is warmed with the heat from a heater disposed below and is kept in a vaporized form within the quartz container.
When the aforementioned wafer is brought into the vapor of IPA, the IPA vapor is cooled and liquefied by the wafer wet with the aforementioned DI water and allowed to trickle down the wafer surface. In the meantime, the moisture adhering to the wafer is displaced with IPA, with the result that this moisture is removed from the wafer surface. In this while, the wafer is gradually heated by the IPA vapor. The liquefaction of IPA ceases to occur when the temperature of the wafer is equalized with that of the IPA vapor.
As the result, the foreign particles which adhere to the wafer during the cleaning with the aforementioned DI water and/or the subsequent step are thoroughly washed out and the wafer surface is brought to a clean, dry state. Subsequently, the cleaned and dried wafer as supported on the carrier is transferred by the movable hanger to a wafer removing part.
As is well known, the space inside the vapor drying apparatus is required to be kept in a clean state lest foreign particles should adhere to the wafer. By this reason, the operator assigned to the job of inserting the wafer-supporting carrier into the vapor drying apparatus has been required to observe the rule of wearing a dustproof work dress and dustproof gloves, for example, while engaging in the operations of opening and closing the wafer insertion door and inserting the carrier through the door into the vapor drying apparatus.
The wafer surface which has undergone the vapor drying treatment assumes a dry state as described above. Microscopically, however, the IPA generally remains in the form of film or in a molecular thickness on the wafer surface. The wafer surface is eventually dried completely because the IPA remaining in the state just mentioned is spontaneously diffused into the ambient air with elapse of time.
The conventional technique described above has had the following disadvantages:
(1) The operator, while transferring the wafer-supporting carrier into and out of the vapor drying apparatus, wears the dustproof dress and other gear in an effort to prevent foreign particles from entering the apparatus. In accordance with the conventional technique, since the aforementioned carrier is directly brought into or taken out of the apparatus manually, there inevitably ensues entry of inorganic and/or organic particles into the apparatus.
(2) On the wafer surface which has undergone the vapor drying treatment, the IPA yet to be spontaneously diffused remains in the form of film or in a molecular thickness as described above. As the result, the wafer fresh out of the vapor drying treatment cannot be immediately subjected to the treatment of the subsequent step. In the conventional operation, therefore, between the time the vapor drying treatment performed on the wafer is completed and the time the subsequent treatment is started, the wafer is required to stand idle until the IPA completes its spontaneous diffusion. Thus, the operations suffers from poor efficiency.
(3) There is the possibility that even after the IPA adhering to the wafer surface fresh out of the vapor drying treatment vanishes as through spontaneous diffusion, organic substances such as carbon will remain fast on the aforementioned wafer surface. It is difficult to bring the wafer surface to a thoroughly cleaned state.